Currently available thermoelectric materials include a type in which conductive layers and barrier layers are layered adjacent to each other and are directly joined to each other (see, for example, U.S. Pat. No. 5,436,467).
In the thermoelectric material, the energy gap in the barrier layer is maintained to be much wider than the energy gap in the conductive layer to create a large difference between the two energy gaps, whereby quantum wells are formed in the conductive layers. As a result, the electric conductivity of the thermoelectric material is heightened, and an improved thermoelectric performance is exhibited.
However, when such a currently available thermoelectric material is subjected to a high temperature condition, the energy gap is broadened in the conductive layer and is narrowed in the barrier layer due to diffusion, mainly, mutual diffusion between the conductive layer and the barrier layer. Accordingly, the difference between the two energy gaps becomes small, making it impossible to form a quantum well in the conductive layer. As such, conventional thermoelectric materials have a low heat resistance and are incapable of maintaining adequate thermoelectric performance under a high temperature condition.
A need therefore exists for an improved thermoelectric material that maintains good performance at high temperatures. The present invention fulfills this need by preventing the occurrence of diffusion between the conductive layer and the barrier layer, and provides further related advantages.